Wearable Tin‐Based Perovskite Solar Cells Achieved by a Crystallographic Size Effect

We developed a size effect that controls the crystallization of perovskite and enhances the passivation effect with g-C3N4 additive. The similarity in value of lattice constant and distance between double hydrogen binding sites affects crystallization. The combination allows g-C3N4 to cover tin-based perovskite, thus improves hydrophobicity and oxidation resistance of films and leads to splendid PCE of wearable device with excellent stability.